HANDS-ON GARDENER: Let’s Talk About Weeds: A Tale of Comeuppance!

Digitaria sanguinalis or crabgrass. Photo courtesy of Miriam Hansen.

Digitaria sanguinalis or crabgrass.
Photo courtesy of Miriam Hansen.

by Miriam Hansen

For most of the 40 years we’ve been gardening, weeding has not been a big onerous issue. When friends have bemoaned the amount of time and effort they spend weeding, I have helpfully (read smugly) offered the following advice:

Cover crop with winter rye to suppress Agropyron repens — common name witch grass, quack grass or couch grass — the plant with the telltale yellowish-white creeping underground stems that can grow from just a tiny piece of stem, and thus, are very hard to get rid of. We have pretty much eliminated witch grass from the vegetable garden by cover cropping with winter rye in fall and tilling it in, in the spring.

Weed often and thoroughly when seedlings are young. Once the plants have matured, their canopy will shade out the weeds. Plant in beds rather than rows and mulch heavily between beds with sheets of newspaper lightly covered with straw or leaves.

Plant closer than the seed packets suggest and interplant with fast growing crops like radishes, kohlrabi, lettuce and arugula to take up the space between the broccoli or Brussel sprouts when they’re young. By the time your principal crop has matured, you’ll have harvested the rapid growers.

And lastly, try to prevent weeds from going to seed. Remember the old adage, “One year’s seeding, seven years weeding.”

Now I don’t regret this advice. It is good advice, if a trifle smugly given. And until now, we’ve never worried too much about the odd plant seeding. Gardening season is demanding and you can’t be everywhere at once. But I’d never had to deal with an infestation of crabgrass!

The scientific name for this unpleasant weed is Digitaria sanguinalis (large crabgrass) or D. ischaemum (smooth crabgrass). As the photo shows, crabgrass has a spreading branching structure and a really impressive root system that does not easily let go. In fact, I suspect that’s where crabgrass gets its name. It’s crabby about being pulled out. Up at the top of the peas, so many seeds have sprouted, the plants have formed a dense mat. It crowds around the foot of other weeds and will root at every node in a process called tillering. This makes weeding it out quite painstaking. The leaves, hairy or smooth depending on the species, turn dark red or maroon as they mature.

The good news is that crabgrass is an annual and is killed by cold. The bad news is that if allowed to flower and set seed, each plant can produce as many as 150,000 seeds that will happily overwinter and come up over the entire course of the growing season. In our garden it is now growing along the fence lines, in the beds, and at the edges of the mulched paths. I’m not sure how it got introduced. Possibly it came in with horse manure we’ve been getting from a neighbor. But I suspect it got a toehold a couple of years ago when we had three weeks of drought followed by six weeks of torrential rains. I think the crabgrass outcompeted all the other weeds. In our ignorance of the havoc it could wreak, we were not sufficiently vigilant about preventing it from going to seed.

When we discovered crabgrass growing in the gravel alongside the driveway and between the paving stones in the walk, I began to panic. And of course panicking does not do much good. This is when I called the state agronomist, Vern Grubinger who reassured me that we are not alone.

He said that weeding with a cobra tool or conventional hoe brings more crabgrass seeds to the surface and suggested we use a collinear hoe, a tool developed by Elliot Coleman and available from Johnny’s Seeds. I ordered two; a three and-a-half-inch and seven-inch blade for use between and within beds. The sharp straight blade cuts about one half an inch below the surface and is used with the same motion you use when sweeping with a broom. The idea is to uproot the young seedlings without bringing more buried seeds up to the surface.

He also suggested mulching heavily wherever possible. We hoed down the buckwheat we’d planted along the fence line and laid down black plastic. He said to use short covers, meaning plant and till cover crops at short intervals. Our experience with buckwheat suggested that the crabgrass would happily live at its feet. Grubinger suggested we try Japanese Millet, applied quite heavily. I ordered a 50-pound bag from Guy’s Farm and Yard and while I waited for them to load it into our car, I noticed that the flower bed adjoining Guy’s parking lot was infested with crabgrass. As Vern said, we are not alone!

We are being very diligent; cultivating frequently, cover cropping, mulching, weed whipping along the outside of fence lines and around greenhouses. It is exhausting! If we weren’t enjoying bumper crops of lettuce, peas, raspberries, carrots and Chinese greens, I might reconsider growing our own food. But I’m addicted to the taste of fresh vegetables from the garden. And I’m already thinking about next year in the crabgrass war; running pigs through the top of the garden, chickens at the bottom and investing in some garden mats for the vegetables we grow in the middle. Let the crabgrass games begin!

In the meantime, happy weeding, gardening and eating!